1. Field of the Invention
The present invention relates generally to manipulator welding apparatus and more particularly to control apparatus utilizing a vision correction system for workpiece sensing for detecting the deviation between a taught welding path and the actual seam to be welded where the welding path is determined relative to a frame of reference defined by the workpiece.
2. Description of the Prior Art
Various welding apparatus and vision detection systems have been proposed. For example, U.S. Pat. No. 4,380,696 which issued to I. Masaki on Apr. 19, 1983 and which is hereby incorporated by reference for all purposes provides a method and apparatus for teaching a welding path with respect to a workpiece at a reference position, moving the manipulator arm in accordance with the taught data during a first repeat pass for successive workpieces and utilizing a vision correction system for determining the deviation between a first repeat pass path and the actual welding path, and moving the manipulator to weld the actual welding path in a second repeat pass in accordance with corrected weld path data obtained by modifying the first repeat pass sensing path data in accordance with the obtained deviation. Further, application Ser. No. 239,621 filed by I. Masaki on Mar. 2, 1981 provides a method and apparatus for detecting any positional and orientational deviation of a workpiece from a reference position by means of a visual detection system and an image processor. Further, U.S. Pat. Nos. 4,348,578 and 4,306,144 disclose arrangements for performing the detection of images of the workpiece either by increasing the vision projector intensity during sensing or by interrupting the welding operation during sensing. Additionally welding apparatus with control arrangements are disclosed in U.S. Pat. Nos. 4,115,684, 4,086,522, 4,030,617, 4,105,937, 3,532,807, 4,148,061, 4,338,672, 3,840,739, 3,766,355, and 4,255,643.
While the above described arrangements are generally suitable for their intended use, there is a constant need for improved welding control apparatus with improved weld path definition for example where the start and end points of a weld path are desirably determined with respect to a workpiece. For example, in the prior art, the start and end point of a weld path must be located a distance away from the corner or edges of a workpiece to account for uncorrected variations in workpiece position tangential to the seam trajectory.